degesch: implement autocompletion for /set

It was super annoying to just slightly modify strings and
string arrays, now you can have existing values filled in.

complete_word() looks a bit cleaner now as well.

degesch.c

@@ -12358,15 +12358,12 @@ completion_locate (struct completion *self, size_t offset)
 	self->location = i - 1;
 }
 
-static bool
+static char *
-completion_matches (struct completion *self, int word, const char *pattern)
+completion_word (struct completion *self, int word)
 {
 	hard_assert (word >= 0 && word < (int) self->words_len);
-	char *text = xstrndup (self->line + self->words[word].start,
+	return xstrndup (self->line + self->words[word].start,
 		self->words[word].end - self->words[word].start);
-	bool result = !fnmatch (pattern, text, 0);
-	free (text);
-	return result;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -12461,6 +12458,66 @@ complete_option (struct app_context *ctx, struct completion *data,
 	strv_free (&options);
 }
 
+static void
+complete_set_value (struct config_item *item, const char *word,
+	struct strv *output)
+{
+	struct str serialized = str_make ();
+	config_item_write (item, false, &serialized);
+	if (!strncmp (serialized.str, word, strlen (word)))
+		strv_append_owned (output, str_steal (&serialized));
+	else
+		str_free (&serialized);
+}
+
+static void
+complete_set_value_array (struct config_item *item, const char *word,
+	struct strv *output)
+{
+	if (!item->schema || item->schema->type != CONFIG_ITEM_STRING_ARRAY)
+		return;
+
+	struct strv items = strv_make ();
+	cstr_split (item->value.string.str, ",", false, &items);
+	for (size_t i = 0; i < items.len; i++)
+	{
+		struct str wrapped = str_make (), serialized = str_make ();
+		str_append (&wrapped, items.vector[i]);
+		config_item_write_string (&serialized, &wrapped);
+		str_free (&wrapped);
+
+		if (!strncmp (serialized.str, word, strlen (word)))
+			strv_append_owned (output, str_steal (&serialized));
+		else
+			str_free (&serialized);
+	}
+	strv_free (&items);
+}
+
+static void
+complete_set (struct app_context *ctx, struct completion *data,
+	const char *word, struct strv *output)
+{
+	if (data->location == 1)
+	{
+		complete_option (ctx, data, word, output);
+		return;
+	}
+	if (data->location != 3)
+		return;
+
+	char *key = completion_word (data, 1);
+	struct config_item *item = config_item_get (ctx->config.root, key, NULL);
+	if (item)
+	{
+		char *op = completion_word (data, 2);
+		if (!strcmp (op, "-=")) complete_set_value_array (item, word, output);
+		if (!strcmp (op,  "=")) complete_set_value       (item, word, output);
+		free (op);
+	}
+	free (key);
+}
+
 static void
 complete_topic (struct app_context *ctx, struct completion *data,
 	const char *word, struct strv *output)
@@ -12514,33 +12571,30 @@ static char **
 complete_word (struct app_context *ctx, struct completion *data,
 	const char *word)
 {
-	// First figure out what exactly we need to complete
+	char *initial = completion_word (data, 0);
-	bool try_commands = false;
-	bool try_options = false;
-	bool try_topic = false;
-	bool try_nicknames = false;
-
-	if (data->location == 0 && completion_matches (data, 0, "/*"))
-		try_commands = true;
-	else if (data->location == 1 && completion_matches (data, 0, "/set"))
-		try_options = true;
-	else if (data->location == 1 && completion_matches (data, 0, "/help"))
-		try_commands = try_options = true;
-	else if (data->location == 1 && completion_matches (data, 0, "/topic"))
-		try_topic = try_nicknames = true;
-	else
-		try_nicknames = true;
 
+	// Start with a placeholder for the longest common prefix
 	struct strv words = strv_make ();
-
-	// Add placeholder
 	strv_append_owned (&words, NULL);
 
-	if (try_commands)   complete_command (ctx, data, word, &words);
+	if      (data->location == 0 && *initial == '/')
-	if (try_options)    complete_option (ctx, data, word, &words);
+		complete_command   (ctx, data, word, &words);
-	if (try_topic)      complete_topic (ctx, data, word, &words);
+	else if (data->location >= 1 && !strcmp (initial, "/set"))
-	if (try_nicknames)  complete_nicknames (ctx, data, word, &words);
+		complete_set       (ctx, data, word, &words);
+	else if (data->location == 1 && !strcmp (initial, "/help"))
+	{
+		complete_command   (ctx, data, word, &words);
+		complete_option    (ctx, data, word, &words);
+	}
+	else if (data->location == 1 && !strcmp (initial, "/topic"))
+	{
+		complete_topic     (ctx, data, word, &words);
+		complete_nicknames (ctx, data, word, &words);
+	}
+	else
+		complete_nicknames (ctx, data, word, &words);
 
+	cstr_set (&initial, NULL);
 	LIST_FOR_EACH (struct hook, iter, ctx->completion_hooks)
 	{
 		struct completion_hook *hook = (struct completion_hook *) iter;